The invention relates to a method of operating a load from alternating current mains, wherein a quantity of energy is withdrawn from the AC current mains in single short switch intervals, is stored temporarily and/or supplied to the load, and wherein each half wave in the AC mains is subdivided into a plurality of switch intervals. In each of these intervals, a cycle elapses during which energy is withdrawn from the AC mains, and using simultaneous intermediate storage, a quantity of energy is delivered to a final store and/or to the load, or vice versa.
For carrying out this known method, use is made mainly of so-called "high set regulators" which are composed of a rectifier circuit, a switch which effects turning on-and-off an inductor that serves as an intermediate store to or from the rectifier circuit, and which is controlled by a regulator circuit, and a capacitor which serves as a final store. Hence, a small quantity of energy is taken from the supply mains in single short switch intervals, is stored temporarily as current in the inductor, and is stored in the capacitor, until it is used up in the load. In this manner, the voltage level is converted from the actual value of the supply mains voltage to the approximately constant voltage value of the storage capacitor.
The regulator circuit forces an approximately sinusoidal variation of the mean value of the current taken from the supply mains. However, in this case, the direct voltage applied to the load is not constant, but exhibits a waviness whose magnitude depends upon the source frequency, the current carried by the load, the load voltage and the magnitude of the storage capacitance.
This makes it possible for the reaction of the operation of a load with rectified alternating current to the alternating current supply mains, particularly the occurrence of harmonics which interfere with other loads, to be kept low. However, it does result in a decisive disadvantage, namely a substantial waviness of the direct current applied to the load or, in order to keep this waviness within limits, the need for very expensive structural components, particularly the storage capacitor. Also, the storage capacitor causes considerable problems because of its large volume and, if it has to be constructed as an electrolytic capacitor, its limited service life.